The present invention relates to flame retardant organopolysiloxane-polycarbonate triblock copolymers which can be made by phosgenating a mixture of a phenol-organopolysiloxane chainstopper and a bisphenol. More particularly, the present invention relates to the use of phenol-organopolysiloxane chainstoppers which can be made by effecting a platinum catalyzed addition reaction between an aliphatically unsaturated phenol and a polyorganosiloxane terminated with a condensed diorganohydrogensiloxy unit.
Prior to the present invention, as shown by copending application Ser. No. 07/455,122, phenol-siloxane macromers were synthesized and used to make flame retardant silicone-polyphenylene ether graft copolymers. There also is shown in U.S. Pat. No. 4,916,194, flame retardant aromatic polycarbonate compositions based on the use of certain poly(arylsilicon) materials in combination with aromatic polycarbonate. Flame retardant thermoplastics and methods for making such materials are constantly being evaluated by the construction and automotive industries to satisfy their requirements for flame retardant injection moldable materials.